BOUNDARY BETWEEN THE PERMIAN AND TRIASSIC ROCKS IN THE MOSCOW SYNECLISE RECONSTRUCTED FROM THE ROCK SEQUENCES EXPOSED IN THE KICHMENGA RIVER BASIN
Rubrics: ORIGINAL ARTICLES
Authors:
1.
Kazan State University, Kazan, Russia
Type:
Article
Pages:
from 107
to 114
Status:
Published
Received:
25.04.2005
Accepted:
25.04.2005
Published:
25.04.2005
Language:
English
Keywords:
Moscow Syneclise, paleomagnetic mineralogical studies, Early Triassic, maghemite-magnetite association .
Abstract (English):
This paper presents the results of the paleomagnetic and magnetic mineralogical studies carried out along the sequence of the recently discovered oldest Nedubrovo Early Triassic rocks of the Moscow Syneclise, exposed in the lower course of the Kichmenga River, where they overlie the Late Permian Vyatkan claystone. The Triassic and Permian rock sequence is composed mostly of silty claystone, containing various fauna and flora remains, including those of terrestrial vertebrates. As reported by V.nbsp;R.nbsp;Lozovskii et al., the argillaceous rocks contain the products of the chemical reworking and relics of some volcanogenic ash material. The Permian-Triassic transition is recorded in the magnetic properties of the rocks by a high two- or three-order of magnitude growth of their magnetic susceptibility and natural remanent magnetization. The most abnormal Permian-Triassic relationship is characteristic of the first layer having a thickness of about 6 m. The data available for the magnetic minerals suggest that characteristic of the Permian claystone is a magnetic goethite-hematite association, and that of the Triassic rocks is a maghemite-magnetite association. The latter is associated genetically with the processes of the low-temperature oxidation of the titanomagnetite. For this reason, the abundance of maghemite and magnetite in the argillaceous rocks of the region is supposed to have been caused by the addition of ash material to the sedimentation basin. The higher values of the magnetic properties of the Early Triassic rocks, compared to the Permian deposits, caused by the presence of maghemite and magnetite, are also characteristic of many other Lower Triassic continental rock sequences in the East of the Russian Platform, and also of the marine rock sequences of South China. In terms of their paleomagnetic properties, the deposits of the Nedubrovo Member show the stable negative polarity of the geomagnetic field.
This paper presents the results of the paleomagnetic and magnetic mineralogical studies carried out along the sequence of the recently discovered oldest Nedubrovo Early Triassic rocks of the Moscow Syneclise, exposed in the lower course of the Kichmenga River, where they overlie the Late Permian Vyatkan claystone. The Triassic and Permian rock sequence is composed mostly of silty claystone, containing various fauna and flora remains, including those of terrestrial vertebrates. As reported by V.nbsp;R.nbsp;Lozovskii et al., the argillaceous rocks contain the products of the chemical reworking and relics of some volcanogenic ash material. The Permian-Triassic transition is recorded in the magnetic properties of the rocks by a high two- or three-order of magnitude growth of their magnetic susceptibility and natural remanent magnetization. The most abnormal Permian-Triassic relationship is characteristic of the first layer having a thickness of about 6 m. The data available for the magnetic minerals suggest that characteristic of the Permian claystone is a magnetic goethite-hematite association, and that of the Triassic rocks is a maghemite-magnetite association. The latter is associated genetically with the processes of the low-temperature oxidation of the titanomagnetite. For this reason, the abundance of maghemite and magnetite in the argillaceous rocks of the region is supposed to have been caused by the addition of ash material to the sedimentation basin. The higher values of the magnetic properties of the Early Triassic rocks, compared to the Permian deposits, caused by the presence of maghemite and magnetite, are also characteristic of many other Lower Triassic continental rock sequences in the East of the Russian Platform, and also of the marine rock sequences of South China. In terms of their paleomagnetic properties, the deposits of the Nedubrovo Member show the stable negative polarity of the geomagnetic field.
Keywords:
Moscow Syneclise, paleomagnetic mineralogical studies, Early Triassic, maghemite-magnetite association .
Moscow Syneclise, paleomagnetic mineralogical studies, Early Triassic, maghemite-magnetite association .
1. Balabanov, The Permian System: Stratigraphy and the History of the Organic World, 1988.
2. Balme, Medd. Groenl., v. 200, no. 6, 1979.
3. Burov, Proc. Intern. Seminar "Paleomagnetism and Magnetism of Rocks'', 2004.
4. Burov, Paleomagnetic Analysis, 1986.
5. Burov, Data on the Stratigraphy of the Upper Permian in the USSR Territory, 1977.
6. Heller, Phys. Earth Planet. Inter., v. 89, 1995.
7. Lozovskii, Izv. Vuzov, Geology and Exploration, no. 3, 2001.
8. Lozovskii, Natura Bresciana, 2001.
9. Shishkin, The Age of Dinosaurs in Russia and Mongolia, edited by M. J. Benton, M. A. Shishkin, D. M. Unwin, and E. N. Kurochkin, 2000.
